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<br />rr01 <br />L."'~.i. <br /> <br />OPERATION AND MAINTENANCE <br /> <br />2., <br /> <br />pioneer tunnel was in satisfactory condition with a mtntnlUm <br />amount of inflow and having a measured water pressure on the <br />main tunnel lining at station 10360+60 of 142 pounds per square <br />inch, The total inflow passing the tunnel station under the surface <br />divide was 250 gallons per minute, and passing Lawrence adit, <br />west of the divide, 325 gallons per minute, A general increase in <br />inflow was noted between Lawrence adit and Potrero shaft, occur- <br />ring from a few spray leaks, from weep holes in the invert, from <br />a new invert break at station 10538+36 with an inflow approxi- <br />mating 100 gallons per minute, and from numerous small leaks. <br />The inflow through Potrero was 100 gallons per minute or less, and <br />no changes of note were found between Potrero and the west portal. <br />The total inflow into the tunnel as measured at the west portal on <br />October 30-31 was :.\,87 cubic feet per second, compared with a <br />similar measurement made November 29, 1~)47 of 2.97 cubic feet <br />per second. <br /> <br />Salt i>1vestigat.ions <br /> <br />The operation and maintenance forces continued to operate two <br />experimental evaporation basins in the vicinity of Danby Dry Lake <br />where the District controls rock salt and brine deposits under a <br />pending U. S. Government lEase. Two basins, one acre and two <br />acres in size. have been in operation since July 1947 and April 1948, <br />respectively, During the year brine was pumped regularly, mea- <br />surements of the salt production were made, and the test brine <br />wells checked, During April 1947, sand protection fences erected <br />on the windward sides of the basins proved successful in keeping <br />out abollt 75 per cent of the blowsand that would have been depos- <br />ited withollt the fences, During April and May 1949, the dike <br />around basin No. 1 was raised about 18 inches to increase the <br />capacity of the basin. Samples of the brine and salt have been <br />sent periodically to the laboratory at the softening and filtration <br />plant for analysis, <br /> <br />Delive)'y of /I'ate)' to the Al'my <br /> <br />Natural Colorado River water was supplied from Lake Mathews <br />to the Uuited States Army at Camp Haan during the entire fiscal <br />year, The maximum monthly delivery was 11,2 acre-feet in July <br />1948, the minimum 1.7 in June 1949, and the total for the year <br />55.3 acre-feet, <br />